Several theoretical methods are available to describe the lepton pair
production in UPC. A widely used method is the EPA or the generalized
EPA (gEPA). The total cross section of \(\gamma \gamma \rightarrow l\overline{l}\) 
has been calculated in EPA in the classical field approximation of
QED [1]}. The original EPA calculations predict
that the position (transverse momentum) of the peak in the transverse
momentum spectrum is less than 20 MeV, inconsistent with the experimental
data [2]}, [3]}, [4]}. Therefore the
generalized EPA was proposed [1]}, [6]}, [7]}, [8]}, [4]}, [10]}, [11]}
to give the correct position of the peak in the transverse momentum
spectrum [8]}, [10]}, [11]}.
